Methods of synthesis of (1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride and intermediates useful therein

ABSTRACT

Provided herein are methods and intermediates for making (1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride, which are useful for the preparation of compounds useful for the treatment of a disease, disorder, or condition associated with the JNK pathway.

This application is a U.S. national stage application of InternationalPatent Application No. PCT/US2016/043511, filed Jul. 22, 2016, whichclaims the benefit of priority to U.S. Provisional Application Ser. No.62/196,363, filed Jul. 24, 2015, which is incorporated herein byreference in its entirety and for all purposes.

FIELD

Provided herein are methods and intermediates for making(1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride, which are usefulfor the preparation of compounds useful for the treatment of a disease,disorder, or condition associated with the JNK pathway.

BACKGROUND

The connection between abnormal protein phosphorylation and the cause orconsequence of diseases has been known for over 20 years. Accordingly,protein kinases have become a very important group of drug targets. (SeeCohen, Nature, 1:309-315 (2002), Gaestel et al. Curr. Med. Chem. 14:2214-223 (2007); Grimminger et al. Nat. Rev. Drug Disc. 9(12):956-970(2010)). Various protein kinase inhibitors have been used clinically inthe treatment of a wide variety of diseases, such as cancer and chronicinflammatory diseases, including rheumatoid arthritis and psoriasis.(See Cohen, Eur. J. Biochem., 268:5001-5010 (2001); Protein KinaseInhibitors for the Treatment of Disease: The Promise and the Problems,Handbook of Experimental Pharmacology, Springer Berlin Heidelberg, 167(2005)).

JNK is a ubiquitously expressed serine/threonine kinase belonging,together with ERK (extracellular-regulated kinase) and p38, to thefamily of mitogen-activated protein kinases (MAPKs). (Kyriakis J M, Sci.STKE (48):pe1 (2000); Whitmarsh A J, et al. Sci. STKE (1):pe1 (1999);Schramek H, News Physiol. Sci. 17:62-7 (2002); Ichijo H, Oncogene18(45):6087-93 (1999)). MAPKs are important mediators of signaltransduction from the cell surface to the nucleus, using phosphorylationcascades to generate a coordinated response by a cell to an externalstimulus by phosphorylation of selected intracellular proteins,including transcription factors. Additionally, JNK also phosphorylatesnon-nuclear proteins, for example, IRS-1, and Bcl-2 family members.(Davis R J, Trends Biochem. Sci. 9(11):470-473 (1994); Seger R et al.,FASEB J.; 9(9):726-35 (1995); Fanger G R et al., Curr. Opin. Genet.Dev.; 7(1):67-74 (1997)).

The elucidation of the intricacy of protein kinase pathways and thecomplexity of the relationship and interaction among and between thevarious protein kinases and kinase pathways highlights the importance ofdeveloping pharmaceutical agents capable of acting as protein kinasemodulators, regulators or inhibitors that have beneficial activity onmultiple kinases or multiple kinase pathways. The compound chemicallynamed2-(tert-butylamino)-4-((1R,3R,4R)-3-hydroxy-4-methylcyclohexylamino)-pyrimidine-5-carboxamide(alternatively named2-[(1,1-dimethylethyl)amino]-4-[[(1R,3R,4R)-3-hydroxy-4-methylcyclohexyl]amino]-5-pyrimidinecarboxamide;and referred to herein as “Compound I”), an inhibitor of the JNKpathway, is disclosed in U.S. Patent Application Publication No.2013/0029987, published on Jan. 31, 2013, International Pub. No. WO2012/145569 and U.S. patent application Ser. No. 14/608,314, filed Jan.29, 2015, the entireties of each of which are incorporated by referenceherein. Accordingly, there remains a need for new processes for thepreparation of Compound I.

Citation or identification of any reference in Section 2 of thisapplication is not to be construed as an admission that the reference isprior art to the present application.

SUMMARY

Provided herein are processes and intermediates useful for thepreparation of Compound I:

having the name2-(tert-butylamino)-4-((1R,3R,4R)-3-hydroxy-4-methylcyclohexylamino)-pyrimidine-5-carboxamide,which is useful for the treatment of a disease, disorder, or conditionassociated with the JNK pathway.

In particular, provided herein are processes for making a compound offormula (A):

having the name (1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride.

Provided is a method for preparing a compound of formula (A),

-   -   comprises the steps of:    -   (a) contacting a compound of formula (1),

-   -   with a compound of formula (2),

-   -   in the presence of a Lewis Acid in a solvent to provide a        compound of formula (3),

-   -   (b) contacting the compound of formula (3) of step (a) with an        aqueous base to provide a compound of formula (4),

-   -   (c) contacting the compound of formula (4) of step (b) with DMF        and a chlorinating agent in an organic solvent, followed by        treatment of the resulting acid chloride derivative with aqueous        ammonia to provide a compound of formula (5),

-   -   (d) contacting the compound of formula (5) of step (c) with an        aqueous solution of NaOH and NaOCl to provide a compound of        formula (6),

-   -   (e) contacting the compound of formula (6) of step (d) with        (+)-dibenzoyl-D-tartaric acid monohydrate in a solvent to        provide a compound of formula (7),

-   -   (f) contacting the compound of formula (7) of step (e) with an        aqueous base, followed by treatment of the resulting free base        with Boc₂O in an organic solvent to provide a compound of        formula (8),

-   -   (g) contacting the compound of formula (8) of step (f) with a        mixture of a reducing agent, a chiral auxiliary and a Lewis acid        in a solvent, followed by treatment with an oxidant in the        presence of a base to provide a compound of formula (9),

and

-   -   (h) contacting the compound of formula (9) of step (g) with a        solution of hydrochloric acid in a solvent to provide the        compound of formula (A). In one embodiment, the Lewis acid of        step (a) is AlCl₃. In a further embodiment, the solvent of        step (a) is DCM. In one embodiment, the base of step (b) is        NaOH. In one embodiment, the chlorinating agent of step (c) is        SOCl₂. In a further embodiment, the organic solvent of step (c)        is DCM. In one embodiment, the solvent of step (e) is MeOH. In        one embodiment, the base of step (f) is NaOH. In a further        embodiment, the organic solvent of step (f) is DCM. In one        embodiment, the reducing agent of step (g) is NaBH₄. In a        further embodiment, the chiral auxiliary of step (g) is        α-pinene. In a particular embodiments, the Lewis acid of        step (g) is BF₃.Et₂O. In another particular embodiment, the        solvent of step (g) is THF. In still another embodiment, the        oxidant of step (g) is H₂O₂. In a specific embodiment, the base        of step (g) is NaOH. In one embodiment, the solvent of step (h)        is IPA.

In certain aspects, Compound I is useful for inhibiting a kinase in acell expressing said kinase, for example JNK1 or JNK2. In other aspects,Compound I is useful for treating or preventing a condition treatable orpreventable by inhibition of a JNK pathway, as described herein. Inanother aspect, Compound I is useful for treating or preventing one ormore disorders selected from interstitial pulmonary fibrosis, systemicsclerosis, scleroderma, chronic allograft nephropathy, antibody mediatedrejection, or lupus. In yet another aspect, Compound I is useful fortreating or preventing liver fibrotic disorders, or diabetes and/ormetabolic syndrome leading to liver fibrotic disorders, as describedherein.

The present embodiments can be understood more fully by reference to thedetailed description and examples, which are intended to exemplifynon-limiting embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a ¹H NMR spectrum of Compound (A) in D₂O.

FIG. 2 depicts an expanded (˜0.2-3.6 ppm) ¹H NMR spectrum of Compound(A) in D₂O.

FIG. 3 depicts a HPLC chromatogram of Compound (A).

FIG. 4 depicts a chiral GC chromatogram of Compound (A).

DETAILED DESCRIPTION Definitions

As used herein, and in the specification and the accompanying claims,the indefinite articles “a” and “an” and the definite article “the”include plural as well as single referents, unless the context clearlyindicates otherwise.

As used herein, and unless otherwise specified, the terms “about” and“approximately,” when used in connection with amounts or weight percentsof ingredients of a process, mean an amount or weight percent that isrecognized by one of ordinary skill in the art to provide an effectequivalent to that obtained from the specified amount, or weightpercent. In certain embodiments, the terms “about” and “approximately,”when used in this context, contemplate an amount or weight percentwithin 30%, within 20%, within 15%, within 10%, or within 5%, of thespecified amount or weight percent.

“JNK” means a protein or an isoform thereof expressed by a JNK1, JNK2,or JNK3 gene (Gupta, S., Barrett, T., Whitmarsh, A. J., Cavanagh, J.,Sluss, H. K., Derijard, B. and Davis, R. J. The EMBO J. 15:2760-2770(1996)).

“Treating” as used herein, means an alleviation, in whole or in part, ofa disorder, disease or condition, or one or more of the symptomsassociated with a disorder, disease, or condition, or slowing or haltingof further progression or worsening of those symptoms, or alleviating oreradicating the cause(s) of the disorder, disease, or condition itself.In one embodiment, the disorder is a condition treatable or preventableby inhibition of a JNK pathway, as described herein. In anotherembodiment, the disorder is selected from interstitial pulmonaryfibrosis, systemic sclerosis, scleroderma, chronic allograftnephropathy, antibody mediated rejection, or lupus. In yet anotherembodiment, the disorder is a liver fibrotic disorder, or diabetesand/or metabolic syndrome leading to liver fibrotic disorders, asdescribed herein. In some embodiments, the disorder is a liver fibroticdisorder, such as non-alcoholic steatohepatitis, steatosis (i.e. fattyliver), cirrhosis, primary sclerosing cholangitis, primary biliarycirrhosis, hepatitis, hepatocellular carcinoma, or liver fibrosiscoincident with chronic or repeated alcohol ingestion (alcoholichepatitis), with infection (e.g., viral infection such as HCV), withliver transplant, or with drug induced liver injury (e.g., acetaminophentoxicity). In some embodiments, “treating” means an alleviation, inwhole or in part, of a disorder, disease or condition, or symptomsassociated with diabetes or metabolic syndrome leading to liver fibroticdisorders, such as non-alcoholic steatohepatitis, steatosis (i.e. fattyliver), hepatitis or cirrhosis, or a slowing, or halting of furtherprogression or worsening of those symptoms. In one embodiment, thesymptom is jaundice.

“Preventing” as used herein, means a method of delaying and/orprecluding the onset, recurrence or spread, in whole or in part, of adisorder, disease or condition; barring a subject from acquiring adisorder, disease, or condition; or reducing a subject's risk ofacquiring a disorder, disease, or condition. In one embodiment, thedisorder is a condition treatable or preventable by inhibition of a JNKpathway, as described herein. In another embodiment, the disorder isselected from interstitial pulmonary fibrosis, systemic sclerosis,scleroderma, chronic allograft nephropathy, antibody mediated rejection,or lupus. In one embodiment, the disorder is a liver fibrotic disorder,or diabetes or metabolic syndrome leading to liver fibrotic disorders,as described herein, or symptoms thereof.

“Patient” or “subject” is defined herein to include animals, such asmammals, including, but not limited to, primates (e.g., humans), cows,sheep, goats, horses, dogs, cats, rabbits, rats, mice, monkeys,chickens, turkeys, quails, or guinea pigs and the like, in oneembodiment a mammal, in another embodiment a human. In one embodiment, asubject is a human having or at risk for having interstitial pulmonaryfibrosis, systemic sclerosis, scleroderma, chronic allograftnephropathy, antibody mediated rejection, or lupus. In another, asubject is a human having or at risk for having liver fibrotic disordersor diabetes or metabolic syndrome leading to liver fibrotic disorders,or a condition, treatable or preventable by inhibition of a JNK pathway,or a symptom thereof.

Compound (A)

As described in U.S. Patent Application Publication No. 2013/0029987,published on Jan. 31, 2013, International Pub. No. WO 2012/145569 andU.S. patent application Ser. No. 14/608,314, filed Jan. 29, 2015, theentireties of each of which are incorporated by reference herein,compounds of formula I can be prepared as shown in Scheme A.

The processes provided herein relate to methods for making a compound offormula (A):

having the name (1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride,and intermediates useful in said processes.

It should be noted that if there is a discrepancy between a depictedstructure and a name given to that structure, the depicted structure isto be accorded more weight. In addition, if the stereochemistry of astructure or a portion of a structure is not indicated with, forexample, bold or dashed lines, the structure or portion of the structureis to be interpreted as encompassing all stereoisomers of it.

Methods for Making Compound (A)

By way of example and not limitation, the compound of formula (A) can beprepared as outlined in Scheme 1 shown below, as well as in the examplesset forth herein.

In one aspect, provided herein are methods for preparing a compound offormula (A):

the methods comprising contacting a compound of formula (9):

with hydrochloric acid in a solvent.

In some embodiments, the solvent is methanol, 2-propanol (IPA), ether ordioxane. In one embodiment, the solvent is 2-propanol (IPA).

In some embodiments, the methods further comprise preparing a compoundof formula (9):

the methods comprising contacting a compound of formula (8):

with a mixture of a reducing agent, a chiral auxiliary and a Lewis acidin a solvent, followed by treatment with an oxidant in the presence of abase.

In one embodiment, the reducing agent is NaBH₄. In another embodiment,the chiral auxiliary is α-pinene. In another embodiment, the Lewis acidis BF₃.Et₂O. In one embodiment, the solvent is THF or EtOH. In anotherembodiment, the solvent is THF. In one embodiment, the oxidant is H₂O₂or oxone. In another, the oxidant is H₂O₂. In one embodiment, the baseis NaOH.

In some embodiments, the methods further comprise preparing a compoundof formula (8):

the methods comprising contacting a compound of formula (7):

with an aqueous base, followed by treatment of the resulting free basewith Boc₂O in an organic solvent, optionally in the presence of a secondbase.

In one embodiment, the aqueous base is aqueous NaOH. In one embodiment,the organic solvent is DCM or ether. In another embodiment, the organicsolvent is DCM. In one embodiment, the second base is triethylamine.

In some embodiments, the methods further comprise preparing a compoundof formula (7):

the methods comprising contacting a compound of formula (6):

with (+)-dibenzoyl-D-tartaric acid monohydrate in a solvent.

In one embodiment, the solvent is methanol.

In some embodiments, the methods further comprise preparing a compoundof formula (6):

the methods comprising contacting a compound of formula (5):

with an aqueous solution of NaOH and NaOCl.

In some embodiments, the methods further comprise preparing a compoundof formula (5):

the methods comprising contacting a compound of formula (4):

with DMF and a chlorinating agent in an organic solvent, followed bytreatment of the resulting acid chloride derivative with aqueousammonia.

In one embodiment, the chlorinating agent is oxalayl chloride or SOCl₂.In one embodiment, the chlorinating agent is SOCl₂. In one embodiment,the organic solvent is DCM.

In some embodiments, the methods further comprise preparing a compoundof formula (4):

the methods comprising contacting a compound of formula (3):

with an aqueous base.

In one embodiment, the base is LiOH or NaOH. In another embodiment, thebase is NaOH.

In some embodiments, the methods further comprise preparing a compoundof formula (3):

the methods comprising contacting a compound of formula (1):

with a compound of formula (2):

in a solvent, in the presence of a Lewis acid.

In one embodiment, the Lewis acid is AlCl₃. In one embodiment, thesolvent is DCM.

Intermediates useful in the processes provided herein include:

Utility of Compound I

Compound I has utility as a pharmaceutical to treat, prevent or improveconditions in animals or humans. In particular, Compound I is activeagainst protein kinases, particularly JNK1 and/or JNK2. Uses of CompoundI are disclosed in U. S. Patent Publication No. 2013/0029987, publishedJan. 31, 2013, which is incorporated by reference herein in itsentirety.

Abbreviations

The following abbreviations are used in descriptions and examples:

ACN: Acetonitrile

Boc: tert-Butoxycarbonyl

n-BuOH: n-Butanol

DBTA: Dibenzoyl-D-tartaric acid

DBU: 1,8-Diazabicyclo[5.4.0]undec-7-ene

DCM: Dichloromethane

DIPEA: N,N-Diisopropylethylamine

DMAc: N,N-Dimethylacetamide

DMF: N,N-Dimethylformide

DMSO: Dimethylsulfoxide

EtOAc: Ethyl acetate

EtOH: Ethanol

GC: Gas Chromatography

IPA: 2-Propanol

IPAc: Isopropyl acetate

LC: Liquid Chromatography

MeOH: Methanol

2-MeTHF: 2-Methyl tetrahydrofuran

MS: Mass spectrometry

MTBE: tert-Butyl methyl ether

NMP: N-Methyl-2-pyrrolidone

NMR: Nuclear magnetic resonance

OR: Optical Rotation

SFC: Supercritical Fluid Chromatography

Tf: Triflate or trifluoromethanesulfonyl

TFE: 2,2,2-Trifluoroethanol

THF: Tetrahydrofuran

SYNTHETIC EXAMPLES

The following synthetic examples, presented by way of illustration andnot limitation, show methods for the preparation of Compound (A).ACD/NAME (Advanced Chemistry Development, Inc., Ontario, Canada) wasused to generate names for chemical structures and Chemdraw(Cambridgesoft, Perkin Elmer, Waltham, Mass.) to draw the chemicalstructures. In certain cases, Chemdraw was used to generate names forchemical structures.

Example 1: Synthesis of (1R,2R,5R)-5-amino-2-methylcyclohexanolhydrochloride

Methyl 4-methylcyclohex-3-enecarboxylate (3)

To a reactor was added DCM (2.5 L) and methyl acrylate (1) (500.0 g) at20-25° C. under an atmosphere of nitrogen. After stirring for 5 min.,the batch was cooled to 0° C., and isoprene (2) (593.4 g) was added over5-10 min. After stirring for 5 min. at 25° C., anhydrous AlCl₃ (116.2 g)was added over 60-90 min. while maintaining the temperature between0-10° C. After stirring at 0-10° C. for 30 min., the batch was graduallywarmed to 25° C. and stirred (≥3 h) at that temperature until HPLCindicated <1% unreacted methyl acrylate (1). Upon completion of thereaction, as indicated by HPLC, the batch was cooled to 0° C. andquenched with HCl solution (250 mL conc. HCl and 1750 mL water) over aperiod of 30-60 min. while keeping the temperature below 10° C. duringthe quenching period. The batch was allowed to warm upto 25° C., and wasfiltered through Hyflo to remove the undissolved solid while rinsing theresidue with DCM (500 mL). The filtrate was extracted with DCM (1 L),and the combined organic layers were successively washed with 5% aqueousNaHCO₃ (1 L) solution and brine (1 L). DCM was distilled out from theorganic fraction at 40-50° C. under atmospheric condition to furnishcrude methyl 4-methylcyclohex-3-enecarboxylate (3) as a brown liquid(˜1200 g, quantitative yield, 85.54% purity by HPLC), which was used forthe next step without purification.

4-Methylcyclohex-3-enecarboxylic acid (4)

To a solution of NaOH (290.4 g NaOH in 1800 mL water) in a reactor at15-20° C. was slowly added 4-methylcyclohex-3-enecarboxylate (3) (1200 gcrude material from above; 895.63 g considering 100% yield), whilekeeping the temperature below 25° C. The batch was gradually warmed to35-40° C. and the resulting clear solution was stirred (≥2 h) at thattemperature until HPLC indicated <1% unreacted intermediate (3). Uponcompletion of the reaction, as indicated by HPLC, the batch was broughtto 25° C. and quenched with water (900 mL). The aqueous mixturecontaining the product was washed with DCM (2×900 mL). The aqueous layerwas cooled to 0-10° C. and acidified with conc. HCl (630 mL) to pH 1-2while keeping the temperature below 20° C. After stirring the mixturefor 10 min. at 20-25° C., the product was extracted from the aqueouslayer with DCM (2×900 mL). The combined organic layers were washed withwater (900 mL). DCM was distilled out from the organic fraction at40-45° C. and the resulting solid mass was vacuum dried for 1 h at40-45° C. to furnish, upon cooling to room temperature,4-methylcyclohex-3-enecarboxylic acid (4) (707.51 g, 86.90% yield basedon HPLC, 85.28% purity by HPLC). The product thus obtained was dissolvedin DCM (750 mL) and used for the next step without purification.

4-Methylcyclohex-3-enecarboxamide (5)

To a reactor containing a solution of 4-methylcyclohex-3-enecarboxylicacid (4) in DCM from above (˜1614 g, containing ˜690 g of intermediate(4)) was added DMF (6.9 mL) at 25° C. under an atmosphere of nitrogen.After stirring the reaction for 5 min., thionyl chloride (673.44 g) wasadded over a period of 30-60 min. while keeping the temperature below20° C. After stirring for 10 min. at 15-20° C., the reaction was warmedto 25-30° C. and stirred (≥2 h) at that temperature until TLC indicated<2% unreacted intermediate (4). Upon completion of the reaction, asindicated by TLC, the solvents were completely distilled out undervacuum. The resulting mixture was vacuum dried for 30 min. at 35-40° C.and then brought to room temperature. The mass thus obtained was slowlyadded over a period of 30-60 min. to an ice-cold solution (0-5° C.) ofaqueous ammonia (2.76 L) in a separate reactor while keeping thetemperature below 10° C. After stirring the reaction mixture for 30 min.at 0-10° C., the resulting residue was filtered off, washed with water,and vacuum dried over air. The product was further dried in an air ovenat 45-50° C. and brought to room temperature to furnish4-methylcyclohex-3-enecarboxamide (5) as an off-white solid (604 g,88.15% yield based on HPLC, 86.55% purity by HPLC), which was used forthe next step without purification.

4-Methylcyclohex-3-enamine (6)

To a solution of NaOH (481.68 g) and water (2.16 L) in a reactor at −5°C. to 5° C. was added slowly a solution of 10.5% w/w sodium hypochlorite(4587.4 g) under an atmosphere of nitrogen. After stirring for 10 min.,4-methylcyclohex-3-enecarboxamide (5) (600 g) was gradually added inportions at −5° C. to 5° C. The reaction was stirred for 6 h at atemperature below 10° C., gradually warmed to 25° C. and stirred (≥5 h)at that temperature until HPLC indicated <5% unreacted intermediate (5).Upon completion of the reaction, as indicated by HPLC, toluene (1.2 L)was added. The mixture was cooled to 0-5° C. and acidified with conc.HCl (1.5 L) to pH 1-1.5 while keeping the temperature below 20° C. Afterstirring for 5 min., the organic layer was separated, and the aqueouslayer was washed with toluene (1.2 L). The aqueous layer was then cooledto 0-5° C., and basified with aqueous NaOH solution (2.0 kg NaOH and1340 mL H₂O) to pH>13 while keeping the temperature below 20° C. Theproduct was extracted with DCM (2×1.5 L), and the combined organiclayers were dried over sodium sulfate and filtered. DCM was distilledout from the filtrate at 40-60° C. under atmospheric conditions. Theresulting residue was cooled to room temperature to furnish4-methylcyclohex-3-enamine (6) (377.4 g, 78.74% yield based on HPLC,85.74% purity by HPLC), which was used for the next step withoutpurification.

(R)-4-Methylcyclohex-3-enamine hemi-dibenzoyl-D(+)-tartarate (7)

A solution of (+)-dibenzoyl-D-tartaric acid monohydrate (1015.3 g) inmethanol (3 L) was gradually brought to reflux. To this refluxingsolution was slowly added a solution of 4-methylcyclohex-3-enamine (6)(300 g) in methanol (300 mL) over a period of 60-75 min. The reactionmixture was refluxed for 2 h and then gradually cooled to 25° C. over4-5 h. After stirring the reaction mixture for an additional 1 h at 25°C., the resulting residue was filtered, washed with methanol, and driedunder vacuum for 30 min. Chiral HPLC of the Boc protected product(prepared by converting an aliquot to the Boc derivative) indicated71.22% of the desired (R)-4-methylcyclohex-3-enaminehemi-dibenzoyl-D(+)-tartarate (7), and 28.72% of the correspondingS-isomer.

The crude product obtained above (˜645 g) was treated with(+)-dibenzoyl-D-tartaric acid monohydrate (123.1 g) and methanol (3.8L), and the resulting mixture was refluxed for 2 h, and then graduallycooled to 25° C. over 4-5 h. After stirring the reaction mixture for anadditional 1 h at 25° C., the resulting residue was filtered, washedwith methanol, and dried under vacuum for 30 min. Chiral HPLC of analiquot of the product that was converted to the BOC derivativeindicated 82.11% of the desired (R)-4-methylcyclohex-3-enaminehemi-dibenzoyl-D(+)-tartarate (7), and 17.82% of the correspondingS-isomer.

The crude product obtained above (˜480 g) was treated with(+)-dibenzoyl-D-tartaric acid monohydrate (93.3 g) and methanol (2.9 L),and the resulting mixture was refluxed for 2 h, and then graduallycooled to 25° C. over 4-5 h. After stirring the reaction mixture for anadditional 1 h at 25° C., the resulting residue was filtered, washedwith methanol, and dried under vacuum for 30 min. The product thusobtained was further dried in air oven at 45-50° C. to furnish(R)-4-methylcyclohex-3-enamine hemi-dibenzoyl-D(+)-tartarate (7) (220.5g, 28.5% yield, 97.81% purity by GC, melting point range: 205.2-206.3°C., OR: +110.0° (C=1% in acetic acid at 25° C.)); chiral HPLC indicated86.88% of the desired R-isomer and 13.12% of the corresponding S-isomer.

(R)-tert-Butyl (4-methylcyclohex-3-en-1-yl)carbamate (8)

To a solution of NaOH (124 g) and water (1200 mL) at 10-20° C. wasslowly added (R)-4-methylcyclohex-3-enaminehemi-dibenzoyl-D(+)-tartarate (7) (300 g) while keeping the temperaturebelow 25° C. After stirring the reaction mixture for 15 min., theresulting free base was extracted from the aqueous layer using DCM(2×300 mL, 1×150 mL). The organic layers were combined, and theresulting solution (˜850 mL) was treated with Boc anhydride (236.8 g) at0-5° C. The reaction mixture was allowed to warm to 25° C., and stirred(≥2 h) at that temperature until HPLC indicated <1% unreactedintermediate (7). Upon completion of the reaction, as indicated by HPLC,water (230 mL) was added, and the mixture was stirred for 10 min. Theorganic layer was separated and washed with 2% aqueous citric acidsolution (230 mL) followed with water (230 mL). DCM was distilled out at30-40° C. under vacuum, and the resulting pale yellow mass was vacuumdried for 30 min. at 40-45° C. to furnish (R)-tert-butyl(4-methylcyclohex-3-en-1-yl)carbamate (8) (216 g, 98.91% yield based onHPLC, 98.36% purity by HPLC), which contained 14.85% of thecorresponding S-isomer as indicated by chiral HPLC. The product thusobtained was taken in THF (437 mL), stirred for 10 min. to obtain aclear solution, and stored under an atmosphere of nitrogen for use inthe next step.

tert-Butyl ((1R,3R,4R)-3-hydroxy-4-methylcyclohexyl)carbamate (9)

To a suspension of sodium borohydride (76.97 g) in THF (1290 mL) at 25°C. was slowly added (−)-α-pinene (582.07 g) over a period of 15 min.under an atmosphere of nitrogen. After cooling the reaction mixture to0-5° C., boron trifluoride etherate (57%, 531.95 g) was added slowlyover a period of 30-60 min. The reaction was allowed to warm to 25° C.,stirred for 8 h, and then treated with the solution of (R)-tert-butyl(4-methylcyclohex-3-en-1-yl)carbamate (8) in THF prepared above (623 g,containing 215 g of (8)). The resulting reaction mixture was stirred (≥3h) at 25° C. until HPLC indicated <1% unreacted intermediate (8). Aftercooling to 0-5° C., the reaction was quenched slowly by adding waterover a period of 30-60 min., followed by subsequent addition of aqueousNaOH (244.15 g NaOH and 716 mL water) and a solution of 48% hydrogenperoxide (432.36 g). The reaction mixture was gradually warmed to 25° C.and stirred for 3 h, after which a solution of sodium thiosulfate (75 gsodium thiosulfate and 75 mL water) was added. After stirring for 30min., a solution of citric acid (254 g of citric acid and 860 mL water)was added, and the mixture was stirred for an additional 30 min. afterwhich ethyl acetate was added (1290 mL). After stirring for 10 min., theorganic layer was separated and the aqueous fraction was extracted withethyl acetate (2×430 mL). The organic layers were combined and thesolvent was distilled out at 40-50° C. under vacuum. The resulting masswas vacuum dried for 1 h to afford quantitative yield of tert-butyl((1R,3R,4R)-3-hydroxy-4-methylcyclohexyl)carbamate (9) (858 g crude),which was used for the next step without purification.

(1R,2R,5R)-5-amino-2-methylcyclohexanol hydrochloride (A)

A mixture of tert-butyl((1R,3R,4R)-3-hydroxy-4-methylcyclohexyl)carbamate (9) from above (853g, containing 233 g of (9)) and IPA-HCl (14% w/w solution; 699 mL) wasstirred (≥2 h) at 25° C. until HPLC indicated <1% unreacted intermediate(9). The solvent was distilled out at 40-60° C. under vacuum. Fresh IPA(233 mL) was added at 40-45° C. and the solvent was again distilled outat 40-60° C. under vacuum. After degassing for 30 min. at 40-60° C., theresulting mass was treated with fresh IPA (699 mL) and the mixture wasstirred under nitrogen at 30-35° C. for 30 min. and then at 0-5° C. foran additional 30 min. The solid product was filtered at 0-5° C. andwashed with chilled IPA. The resulting product was dried under vacuum at40-60° C. to afford ˜70 g crude product, which contained ˜96.49% of thedesired RRR-isomer as indicated by chiral GC (other isomers were presentas impurities in the amount of 2.06% (SSS isomer), 0.18% (SRR isomer),and 1.26% (RSS isomer)). IPA (3 L) was added and the resulting slurrywas refluxed for 30 min. The mixture was gradually cooled to 70-75° C.,and the undissolved impurity was filtered off and washed with IPA (140mL). The solvent was distilled out at 40-60° C. to afford a white masswhich was gradually cooled to 25° C. and then treated with water (31.5mL) and acetonitrile (31.5 mL). The resulting mixture was heated at75-80° C. for 10 min. to obtain a clear solution, which was then treatedslowly with acetonitrile (574 mL) at 75-80° C. over a period of 1 h.After stirring for 15 min. at 75-80° C., the resulting mass was cooledto 0-5° C. over 2-3 h and stirred at that temperature for 30 min. Theproduct was filtered under nitrogen at 0-5° C., and the solid cake waswashed with chilled acetonitrile (70 mL) and dried under vacuum toafford the desired RRR isomer. The above process of precipitating thedesired product out of a mixture of water and acetonitrile by additionof acetonitrile at 75-80° C. was repeated until chiral-GC indicated thepresence of no more than 0.5% of any other single isomer (SSS, SRR andRSS isomer). The product thus obtained was further dried under vacuum at40-60° C. to afford (1R,2R,5R)-5-amino-2-methylcyclohexanolhydrochloride (A) as a white solid (63 g, 37.4% yield, 100% purity byHPLC, melting point range: 244.0-245.5° C., SOR: −31.2° (C=1% in MeOH at25° C.)); chiral GC indicated 99.83% of the desired RRR-isomer and 0.17%of the corresponding SSS-isomer. ¹H-NMR (D₂O) (400 MHz): δ 3.18-3.08 (m,2H), 2.15-2.12 (m, 1H), 1.86-1.83 (m, 1H), 1.72-1.68 (m, 1H), 1.32-1.16(m, 3H), 1.02-0.91 (m, 1H), 0.86-0.85 (d, 3H, J=6.4 Hz)

A number of references have been cited, the disclosures of which areincorporated herein by reference in their entirety.

What is claimed is:
 1. A method for preparing a compound of formula (A),

the method comprising the steps of: (a) contacting a compound of formula(1),

with a compound of formula (2),

in the presence of a Lewis Acid in a solvent to provide a compound offormula (3),

(b) contacting the compound of formula (3) of step (a) with an aqueousbase to provide a compound of formula (4),

(c) contacting the compound of formula (4) of step (b) with DMF and achlorinating agent in an organic solvent, followed by treatment of theresulting acid chloride derivative with aqueous ammonia to provide acompound of formula (5),

(d) contacting the compound of formula (5) of step (c) with an aqueoussolution of NaOH and NaOCl to provide a compound of formula (6),

(e) contacting the compound of formula (6) of step (d) with(+)-dibenzoyl-D-tartaric acid monohydrate in a solvent to provide acompound of formula (7),

(f) contacting the compound of formula (7) of step (e) with an aqueousbase, followed by treatment of the resulting free base with Boc₂O in anorganic solvent to provide a compound of formula (8),

(g) contacting the compound of formula (8) of step (f) with a mixture ofa reducing agent, a chiral auxiliary and a Lewis acid in a solvent,followed by treatment with an oxidant in the presence of a base toprovide a compound of formula (9),

and (h) contacting the compound of formula (9) of step (g) with asolution of hydrochloric acid in a solvent to provide the compound offormula (A).
 2. The method of claim 1, wherein the Lewis acid of step(a) is AlCl₃.
 3. The method of claim 1, wherein the solvent of step (a)is DCM.
 4. The method of claim 1, wherein the base of step (b) is NaOH.5. The method of claim 1, wherein the chlorinating agent of step (c) isSOCl₂.
 6. The method of claim 1, wherein the organic solvent of step (c)is DCM.
 7. The method of claim 1, wherein the solvent of step (e) isMeOH.
 8. The method of claim 1, wherein the base of step (f) is NaOH. 9.The method of claim 1, wherein the organic solvent of step (f) is DCM.10. The method of claim 1, wherein the reducing agent of step (g) isNaBH₄.
 11. The method of claim 1, wherein the chiral auxiliary of step(g) is α-pinene.
 12. The method of claim 1, wherein the Lewis acid ofstep (g) is BF₃.Et₂O.
 13. The method of claim 1, wherein the solvent ofstep (g) is THF.
 14. The method of claim 1, wherein the oxidant of step(g) is H₂O₂.
 15. The method of claim 1, wherein the base of step (g) isNaOH.
 16. The method of claim 1, wherein the solvent of step (h) is IPA.